Split collets

Well Known and Active Website User

Are split collets for series A valves available anywhere? Also any reason why they are not on the " alternative drawings" I purchased a while ago? All three of my engines where purchased from a "professional dismantler " so was not aware of their need until rebuilding

Well Known and Active Website User

Hi Andy,
If you mean the Alternative Spares List (for Series A machines) put together by Bill Parr, then they do show the split collets (E36) on the exploded head diagram on Page 15.
I bought some years ago from Conways so I assume they'll still have them...
Peter B

Well Known and Active Website User

B,C,&D collets are the same but with a circlip groove turned in them. I had a lot of NOS from Tony Fox-Mail in Norfolk in 1967 or 8 when I loaded an "A" Comet in bits into my Stieb sidecar then called in at Swindon to pick up a "C" Comet for nothing and laid it on top of the sidecar. arriving home in the early hours.

Well Known and Active Website User

Well Known and Active Website User

I've not delved in any depth in to the differences between 'A' collets and post-war ones. However, Bob Stafford in MPH 503 states that "C Collets are shorter than the A variety". Also in his Ab Initio articles, Bob states "Note that C Collets have a seating in them for a wire circlip and cannot be used with Series A valves, which require the correct square-faced collet to sit on the shoulder on the valve stem". See also pages 242 and 243 in the book Back to 'A'.
Peter B

Well Known and Active Website User

I would be most grateful if you could spare two pairs Marcus, I do not intend to rebuild the third engine I have, just doing the correct engine for the frame and a spare will see me out, let me know how to proceed and thanks a bunch

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Well actually no, Marcus, it's not my knowledge; I was merely quoting the findings and knowledge of the late great Bob Stafford.

But the Series 'A' spring collet issue doesn't end here. I have several crusty old used (original?) valves and some old stock new ones too. All have the correct "squared" 90 degree interface between the large and small stem diameters to take the correct "squared top" collets. Great.

But I also have some new Series 'A' valves which I purchased in the UK about 2 to 3 years ago. These are most probably manufactured by the G & S valve company. However, whoever got them made(?), forgot to specify the need for the stem interface to be square; what they actually have is a small taper for about 1/32". So, if you intend to use standard 'A' collets on a standard set-up (and why wouldn't you?), each valve needs that tiny taper machining square on a lathe with a very sharp tool.

Anyone in the process of, or about to start, head-building - would be wise to check what they have in respect of collets and valves.

Well Known and Active Website User

Have located them but looks like I've machined all the pairs I had for circlip wires for B,C & D's but as Peter B says there is a difference from original to new ones with a radius at the shoulder ( which is better as not so much a stress point) with them being machined it should bridge the radius would it not ! ?
Also have plenty of 1/2 ones but with carful measuring should be able to make a pair.

Well Known and Active Website User

Well actually no, Marcus, it's not my knowledge; I was merely quoting the findings and knowledge of the late great Bob Stafford.

But the Series 'A' spring collet issue doesn't end here. I have several crusty old used (original?) valves and some old stock new ones too. All have the correct "squared" 90 degree interface between the large and small stem diameters to take the correct "squared top" collets. Great.

But I also have some new Series 'A' valves which I purchased in the UK about 2 to 3 years ago. These are most probably manufactured by the G & S valve company. However, whoever got them made(?), forgot to specify the need for the stem interface to be square; what they actually have is a small taper for about 1/32". So, if you intend to use standard 'A' collets on a standard set-up (and why wouldn't you?), each valve needs that tiny taper machining square on a lathe with a very sharp tool.

Anyone in the process of, or about to start, head-building - would be wise to check what they have in respect of collets and valves.

Well Known and Active Website User

Not sure these photos will do them justice, but here's a sample, numbering from the left:-
1 & 2 = crusty, decades-old valves (square).
3 = new valve, (square), bought about 2005/6 during Colin Jenner's custodianship of Conways.
4 = new valve, (taper), bought around 2016/17 (can't be sure who from).

As an aside, from the marks on the old valves, I would estimate the split collets used were 1/4" high.

Well Known and Active Website User

I have old valves just like Peters with square cut stems. I have two new valves from the club which are tapered. I suggest the club checks the stock and corrects this if it’s still an issue. I bought them about 2 years ago and have not looked at them. My collets came from Conways and are correct.

Well Known and Active Website User

Here you are Andy,
Back row 2 NOS inlets (50 + years that I've had them) 2 used v/v's
front row two used and one new in last twenty years. with mandrel to machine collets
note : all v/v's have 5/16" dia upper stem, all my inlets have 11/32" lower stem dia and exhaust's have 3/8" dia stems
None of them have a sharp 90 degree at the change of diameter
assorted collets with four shiny new pair from VOCSC and Andy's pair in an envelope ready to be posted.
Now you know what rubbish I hang onto.
bananaman.

Well Known and Active Website User

Not sure these photos will do them justice, but here's a sample, numbering from the left:-
1 & 2 = crusty, decades-old valves (square).
3 = new valve, (square), bought about 2005/6 during Colin Jenner's custodianship of Conways.
4 = new valve, (taper), bought around 2016/17 (can't be sure who from).

As an aside, from the marks on the old valves, I would estimate the split collets used were 1/4" high.

Excellent detail Peter thank you, I also have approx 12 used valves mostly according to your research,are old stock, fortunately I have at least one good pair that I have had refinished. Thank you for your knowledge and time.

Well Known and Active Website User

Here you are Andy,
Back row 2 NOS inlets (50 + years that I've had them) 2 used v/v's
front row two used and one new in last twenty years. with mandrel to machine collets
note : all v/v's have 5/16" dia upper stem, all my inlets have 11/32" lower stem dia and exhaust's have 3/8" dia stems
None of them have a sharp 90 degree at the change of diameter
assorted collets with four shiny new pair from VOCSC and Andy's pair in an envelope ready to be posted.
Now you know what rubbish I hang onto.
bananaman.

I will enjoy buying you a beer if I get the pleasure of your company Marcus, look me up if in Melbourne. I will be travelling to Liverpool and Portsmouth in March for a reunion of my old RN colleagues and hope to call in at the new club rooms on my travels. Thanks a bunch.